﻿// https://leetcode-cn.com/problems/validate-binary-search-tree/
// 98. 验证二叉搜索树

#include <iostream>
#include <vector>
#include <string>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <queue>
#include <limits.h>

using namespace std;

// struct ListNode {
//     int val;
//     ListNode *next;
//     ListNode() : val(0), next(nullptr) {}
//     ListNode(int x) : val(x), next(nullptr) {}
//     ListNode(int x, ListNode *next) : val(x), next(next) {}
// };

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

class Solution {
public:
    bool isValidBST(TreeNode* root) {
        vec.clear();
        traversal(root);
        for (int i = 1; i < vec.size(); i++) {
            if (vec[i] <= vec[i - 1]) return false;
        }
        return true;
    }
private:
    vector<int> vec;
    void traversal(TreeNode* root) {
        if (root == NULL) return;
        traversal(root->left);
        vec.push_back(root->val);
        traversal(root->right);
    }
};

int main() {
    Solution obj = Solution();
}